高密度聚乙烯装置聚合釜生产能力评估

研究了高密度聚乙烯（ＨＤＰＥ）装置聚合釜生产能力的影响因素,通过自行编制的计算机程序对聚合系统进行了模拟,研究了在现有生产条件下,聚合釜的最大生产能力,并指出了提高生产能力的途径。     

高密度聚乙烯装置反应器飞温原因分析及对策

反应器飞温会严重影响高密度聚乙烯装置的正常生产。文章介绍了中韩石化武汉乙烯高密度聚乙烯装置聚合反应单元的主要工艺流程,叙述了该装置反应器飞温事故过程,分析得出反应器内聚合反应过于剧烈和夹套水系统失去冷却功能是造成反应器飞温的根本原因,并提出了相应的应急处理方法及预防措施。     

氢气PSA在高密度聚乙烯装置中的应用

文章结合武汉乙烯高密度聚乙烯装置生产的实际情况,介绍了氢气PSA系统在该装置的应用,探讨了该系统投用与否对装置生产的影响。     

乙烯淤浆聚合反应器的模型与模拟

建立了乙烯淤浆聚合反应器的多相全混流模型,描述了包括乙烯共聚合反应动力学、气液和液固传质、反应器传热在内的物理化学过程。通过模拟计算分析了聚合过程的控制步骤,得到了反应器生产能力与有关操作变量之间的关系,对某工业反应器的模拟结果表明计算值与生产数据具有很好的一致性。     

稳态反应模型在气相聚乙烯反应器中的应用

通过对气相流化床聚乙烯工艺稳态反应模型的应用进行分析，讨论了中间控制参数温度、氢气乙烯摩尔比、共聚单体乙烯摩尔比、催化剂产率等输入变量对反应器输出变量树脂性能－熔体流动指数（MI）的影响。选择工业实例，对系统出现波动后人工调控MI与利用稳态反应模型的计算机调控MI的过程分别进行了计算，并对2种调控过程进行了比较，证明了稳态反应模型在工业质量控制中的优越性。     

高密度聚乙烯的研究及应用

综述了近年来我国高密度聚乙烯(HDPE)的最新研究现状,并介绍了高密度聚乙烯的特点及其应用,最后指出了我国高密度聚乙烯的发展方向。     

高密度聚乙烯装置扩容改造评述

北京燕化石油化工股份有限公司化工一厂高密度聚乙烯装置扩容改造项目是该公司１９９８年安排的１０个效益增长点之一。本文介绍了该项目的背景和工作开展情况,包括装置瓶颈分析、设备核算、改造内容的确定、相关的技术工作等,评述了改造的经验和效果。     

高密度聚乙烯MLE在布面胶鞋中的应用

高密度聚乙烯ＭＬＥ能部分代替布面胶鞋橡胶部件中的天然橡胶，同时改善工艺性能和降低成本。对胶料物理机械性能也有影响，其中硬度明显上升，耐屈挠性、磨耗变化很小，拉伸强度、扯断伸长率等随其用量增加而降低，因此有一定的使用范围。     

无机阻燃剂在高密度聚乙烯阻燃格栅中的应用

将无机阻燃剂聚磷酸铵、氧化锑添加到高密度聚乙烯中,制得阻燃格栅材料,通过氧指数法和燃烧试验测得了其阻燃效果,并得出了最佳的阻燃剂添加量。     

Modeling of branching density and branching distribution in low-density polyethylene polymerization

Low-density polyethylene (ldPE) is a general purpose polymer with various applications. By this reason, many publications can be found on the ldPE polymerization modeling. However, scission reaction and branching distribution are only recently considered in the modeling studies due to difficulties in measurement and computation of scission effect and branchings of polymer. Our previous papers [Kim, D.M., et al., 2004. Molecular weight distribution modeling in low-density polyethylene polymerization; impact of scission mechanisms in the case of CSTR. Chemical Engineering Science 59, 699-718; Kim, D.M., Iedema, P.D., 2004. Molecular weight distribution modeling in low-density polyethylene polymerization; impact of scission mechanisms in the case of a tubular reactor. Chemical Engineering Science, submitted for publication] are concerned with the scission reaction during ldPE polymerization and its effect on molecular weight distribution (MWD) of ldPE for various reactor types. Here we consider branching distributions as a function of chain length for CSTR and tubular reactor processes. To simultaneously deal with chain length and branching distributions, the concept of pseudo-distributions is used, meaning that branching distributions are described by their main moments. The computation results are compared with properties of ldPE samples from a CSTR and a tubular reactor. Number and weight average branchings and branching density increase as chain length increases until the longest chain length. The concentrations of long chain branching (LCB) are close to those of first branching moment in both CSTR and tubular reactor systems. The branching dispersity, a measure for the width of the branching distribution at a certain chain length, has the highest value at shorter chain length and then monotonously decreases approaching to 1.0 as chain length increases. Excellent agreements in branching dispersities between calculation with branching moments and prediction with assumption of binomial distribution for a tubular reactor and CSTR processes show that the branching distribution follows a binomial distribution for both processes.     

Modeling of industrial high pressure autoclave polyethylene reactor including decomposition phenomena

The aim of the present work is the development of a practical model for an industrial high-pressure polyethylene plant. The reactor considered in this work is the adiabatic slim type autoclave with four zones for free radical polymerization of ethylene. A fairly comprehensive but realistic model is described that has the ability to predict the temperature at each reaction zone as well as the effects of initiator flow changes. From the stability analysis we could identify the range of operating conditions which can effectively be used to prevent decomposition phenomena (runaway reactions) and to maximize polymer conversion in LDPE autoclaves.     

状态估计技术及其在聚合反应器控制中的应用

介绍了在线检测技术和状态估计技术，及利用状态估计技术获取单体转化率、聚合物相对分子质量分布和组成等产品特性，实现聚合反应器的在线控制的应用。     

Stress-Cracking of high density polyethylene in detergents

Correlations of the stress intensity factor, K_I, with crack speed, ?, have been obtained in a number of detergent solutions each having different detergent concentration. A constant crack speed region was observed in high density polyethylene. The K_I independent constant crack speed was found to vary linearly with detergent concentration. The viscosity of the detergent solution increases with concentration and hence this region is not controlled by the hydrodynamic properties of the environment in contrast with Williams' model. The K_I-? data were compared with existing models of crack propagation.     

Thermal and morphological evaluation of very low density polyethylene/high density polyethylene blends

Blends of very low density polyethylene (VLDPE) and high density polyethylene (HDPE) were prepared by melt extrusion. These blends exhibit a tendency to phase segregate when they are slow cooled from the melt. If they are cooled at increasingly faster rates, a finite population of co‐crystals can be isolated from the rest of the phase segregated material, indicating that this system is probably miscible in the melt but phase separates during cooling. Transmission electron microscopy observations are consistent with the blend melt miscibility since inter‐lamellar mixing was clearly appreciated in the samples examined. Other effects arising from interactions between the polymers were the nucleation of VLDPE rich phase by HDPE rich phase, and a melting point depression of HDPE rich phase caused by a dilution effect exerted by molten VLDPE rich phase. After a successive self‐nucleation and annealing thermal fractionation procedure is applied to the blends, phase separation dominates the behavior, although some small fraction of co‐crystals was still present.     

Impact yielding of high density polyethylene

We have used a projectile impact method to estimate the flow stress of high density polyethylene at a strain rate of 3 × 10³ sec⁻¹. The technique was developed initially by Taylor and applied successfully by Whiffin and others to ductile metals. The data from this experiment have been compared with data obtained in more conventional compression and drop hammer tests at lower strain rates at 20° and 100°C. The flow stress of high density polyethylene deduced from the impact test at 20°C is significantly higher than that anticipated from a simple extrapolation of the low strain rate data at 20°C. The data at 100°C are however in good agreement. The technique has also been used to estimate the flow stress of high density polyethylene as a function of temperature over the range −20° to +105°C. These data indicate that the discrepancy in the data for 20°C arises from a real discontinuity in the response of the polymer rather than from an inadequacy in the theoretical analysis of the impact experiment as applied to polymeric solids. We conclude that the impact method described is a useful technique for estimating the flow stress of polymers. It is however limited to a relatively narrow range of strain rates.     

Inhomogeneous deformation in welded high density polyethylene

The effect of the thermal history on the properties of welded high density polyethylene is studied. The lamellar microstructure observed in the weld is different from that in the bulk slow cooled material. The weld has lower crystallinity and smaller lamellar size, both of which change with annealing. The differences in the microstructure between the weld and the surrounding material produce differences in the plastic properties. The low ductility of the welded samples is a direct result of the relatively low yield stress within the weld. Annealing of the weld can improve the tensile properties, but in quenched welds the final properties are still inferior to the bulk material. Displacement controlled, constant velocity microindentation tests are shown to provide a rapid means of evaluating the properties of the weld. © 2002 Wiley Periodicals, Inc. J Appl Polym Sci 86: 43–52, 2002     

Solubility and diffusivity of cyclohexane in high density polyethylene

The diffusivity and solubility of cyclohexane in a high density polyethylene, HDPE, were studied using a gravimetric, quartz‐spring, sorption balance. Solvent concentrations up to a weight fraction of 0.15 over a temperature range of 90 to 160°C were measured. Diffusion coefficients in the range of 10^?6 to 10^?7 were determined. Two types of polymer samples were used: a commercial bead form and flat sheets prepared by melting the polymer. Within the experimental error no differences were observed between the two forms indicating that there were no significant effects caused by the melting and compression. The solubility of cyclohexane in the HDPE as a function of the activity of the cyclohexane was linear. Above the melt temperature the solubility data were predicted better by the group‐contribution, lattice‐fluid equation of state (GCLF‐EoS) than by the van der Waals free‐volume (UNIFAC‐vdw‐FV) model. Below the melt temperature a correction factor for the elasticity significantly improved the predictions for both models. Although the HDPE has a crystallinity of 77.6%, the experimental data and the Vrentas‐Duda free‐volume theory indicated no significant tortuosity effects. © 2011 Wiley Periodicals, Inc. J Appl Polym Sci, 2012     

Failure sensitivity of high density polyethylene in compression

As part of an investigation of the compressive mechanical behavior of high density polyethylene between room temperature and the crystalline melting temperature, the strain-to-failure as a function of temperature and strain rate was studied. The two resins studied in applied-strain-rate tests were found prone to fail, as judged by decreased strain-to-failure, at temperatures from 70 to 88°C. The strain-to-failure decreased as the temperature was increased or as the strain rate was decreased. This behavior is opposite to that observed in tension at lower temperatures. At temperatures just below melting, the strain-to-failure apparently began to increase again. By analogy to the results of tearing experiments on polyethylene and other thermoplastics, the findings are explained in terms of the influence of the α relaxation in polyethylene. Differences in the behavior of the two polyethylene resins were also examined.